Vitamin D2 increases calcium absorption by as much as 30 to 80 percent. The Osteoporosis Society of Canada recommends that Canadians aged 19 to 50, including pregnant or lactating women, receive 400 international units (IUs) of vitamin D2 per day. Adults over 50 should receive 800 IUs.

Milk fortified with vitamin D2 contains 100 IUs per 250 ml glass. Foods such as margarine, eggs, chicken livers, salmon, sardines, herring, mackerel, swordfish and fish oils (halibut and cod liver oils) all contain small amounts.
Since it may be difficult to get enough vitamin D2 from food alone, you may wish to consider supplements. Most multi-vitamins provide 400 IUs of vitamin D2. Some calcium supplements also contain vitamin D2.

When you can't get enough calcium from food

If you find it difficult to obtain the recommended amounts of calcium through diet alone, a combination of foods rich in calcium and calcium supplements is a good strategy.

Calcium supplements are tablets, capsules or liquids containing the mineral calcium from a non-food source. These sources include:

• Calcium carbonate, which can be refined from limestone, natural elements of the earth, or may come from shell sources, usually oyster. Shell sources are often described on the label as a "natural" source. Calcium carbonate from oyster shells is not "refined" and can contain variable amounts of lead.
• Chelated calcium, which refers to a special way in which calcium is chemically combined with another substance. Calcium citrate is an example of such a chelated preparation. Calcium may also be combined with other substances to form preparations such as calcium lactate or calcium gluconate.
• Powdered bone (bonemeal) or dolomite, a mineral found in rock. (Bonemeal is not recommended, as it may contain contaminants.)